Liver graft preservation injury is a major problem complicating liver transplantation. Preservation injury represents a hypothermic ischemia/reperfusion (I/R) injury. Although all donor livers exhibit some degree of preservation damage, patients receiving grafts with severe preservation injury have poor early liver function and are more susceptible to a variety of complications. The initiating events that account for local organ damage are only partially understood. Interferon regulatory factor-1 (IRF-1) is a nuclear transcription factor originally identified as one of the key factors responsible for interferon beta gene expression (IFN(3), as well as other interferon-inducible genes. IRF-1 is now known to regulate the expression of a number of genes involved in both innate and acquired immunity. Recent data from our group demonstrates that IRF-1 is upregulated after warm hepatic I/R and contributes to tissue damage. However, its function in liver transplantation is unknown. Our preliminary data show that IRF-1 is induced early after liver transplantation, and is also upregulated in primary human hepatocytes after hypoxic stimulation. Further, we identify novel roles forTLR4 and HMGB1 in the IRF-1 signaling cascade. In this proposal, we will pursue three aims to characterize the role and regulation of IRF-1 in liver transplant injury. Our hypothesis is that IRF-1 is a key regulator of the inflammatory response that occurs as a result of liver transplant I/R. Further, we believe that the non-parenchymal antigen-presenting cells (ARC) are crucial for the activation of hepatocellular IRF-1 expression, which then contributes to the liver graft injury. AIM I: To identify the signaling pathways and role of APC in regulating hepatic IRF-1 expression. AIM II: To elucidate the mechanisms of IRF-1 mediated liver injury. AIM III: To determine if IRF-1 blockade can ameliorate liver transplant I/R injury. The information gained by studying the mechanisms of IRF-1 modulation of inflammatory mediators will increase our understanding of the molecular pathophysiology of liver injury. Examining the cross-talk between hepatocytes and non-parenchymal cells (NPCs) for IRF-1 activation will give insight into the early signaling events that result in liver graft damage seen with hepatic transplantation. In addition, by investigating the mechanisms of IRF-1 - mediated liver injury, potential strategies for targeting IRF-1 may be developed to minimize organ damage in the transplant setting. RELEVANCE (Seeinstructions): Liver ischemia / reperfusion injury remains a major problem in hepatic transplantation, particularly with the use of older or expanded criteria donor livers with increased incidence of primary non-function or delayed graft function. Elucidating the upstream molecular mechanisms responsible for ischemic liver transplant injury may lead to clinical strategies aimed at reducing organ damage. This could significantly impact patients in the early post-transplant period, as well as increase the ability to use expanded criteria donor livers to combat the organ shortage crisis.